1. Field of the Invention
The present invention relates to a suspension system used in a vehicle such as are automobile.
2. Description of the Related Art
Steel leaf springs or coil springs have conventionally been used as suspension springs for vehicles. Conventional vehicular suspension systems, which are typified by McPherson struts and double wishbones, comprise steel compression coil springs for suspension, used to support the sprung weight, and suspension arms extending in the transverse direction of the vehicle body. The suspension arms, which are rigid bodies, are mounted on the vehicle body by means of pivots so that they can vertically swing around the pivots. A hub carrier is mounted on the distal end portion of each suspension arm.
The suspension coil springs, which are disposed so that their axes extend in the vertical direction, have a great upward projection. Therefore, spaces for storing the upper portions of the suspension springs are needed in the trunk room, engine room, etc. This results in a narrow interior space of the vehicle.
To cope with these circumstances, the inventors hereof have been developing cantilever spring arms to be used in place of the suspension springs. An FRP (fiber-reinforced plastic) spring ar is formed of a matrix resin and fibers. A fixed end of the spring arm is fixed to the vehicle body. A hub carrier or other means for supporting a wheel is attached to a free end of the arm. The spring arm car bend in the vertical direction.
Since the spring arm extends in the transverse direction of the vehicle body, it sometimes lacks in rigidity to stand a load acting in the longitudinal direction. To cope with this problem, the inventors hereof have proposed an arrangement such that a metallic reinforcing rod, for use as a rigid body, is combined with the spring arm. One end of the reinforcing rod is connected to the free end of the arm. The other end of the reinforcing rod is connected to the vehicle body by means of a bracket disposed in front or at the back of the fixed end of the arm. With use of this reinforcing rod, a load acting on the spring arm in the longitudinal or transverse direction can be reduced. If this metallic reinforcing rod is used in a suspension system, however, the whole system is heavy in weight.
If the rigid metallic reinforcing rod is connected to the FRP spring arm, which is not a rigid body, the spring ar should be prevented front being hindered by the reinforcing rod as it bends in the vertical direction. Thus, the junction between the spring arm and the reinforcing rod has a complicated construction.